Christopher Shinn's new play is a theatrical paradox: it's Shavian but snappy. Only 70 minutes, and pungently written, it's packed (over-packed) with debate. It has a persuasive emotional aspect; the ending, finely staged by Dominic Cooke, is a well-judged surprise. And it's cannily scheduled: its concerns could hardly be more current.

On the eve of a US election, the gay son of the Democratic presidential candidate goes to a party dressed as Muhammad. His dad's supporters think he should apologise before video material becomes public. The boy argues he was acting in the interests of free speech, to expose a fellow student who wanted to censor satire directed at Islam. But he's also rebelling because of his family history: even his birth, he claims, was a media-sensitive decision by his parents.

In researching Now or Later, Shinn was helped by meetings with Cherie Blair and Hillary Clinton's head of communications. Matthew Marsh is very good as the about-to-be-President, suggesting the lustre of power as well as its damage; Eddie Redmayne, volatile and coltish, vividly projects distress and intelligence. Still, there's a hole at the centre: this boy, who's spent a lifetime complaining about his parents' way of going on, is now supposed to be astonished by their response to his actions.

Kicking A Dead Horse is American writing at its posturing cowboy worst: Beckett in a stetson. This Abbey Theatre production of Sam Shepard's play, written for Stephen Rea, features a Manhattan art dealer who, having chucked his canvases out of the window, decides to head for the Badlands so that he can bray about Authenticity. His horse (and who can blame him?) pops his horseshoes, and spends the evening with his plastic-looking hoofs in the air. A girl in a mini-dress comes up from a fissure to simper. All Rea has to do is grumble. He does so with lovely, lugubrious confidentiality, but it's impossible to make these speeches interesting. Talk about flogging a supine equine.